question_answer 1)

Explain why (a) The blood pressure in humans is greater at the feet than at the brain. (b) At morphemic pressure at a height of about 6 km decreases to nearly half its value at the sea level, though the height of the atmosphere is more than 100 km. (c) Hydrostatic pressure is a scalar quantity even though pressure is force divided by area, and force is a vector.

Answer:

(a) The height of the blood column in the human body is more at feet than at the brain. That is why, the blood exerts more pressure at the feet than at the brain.(\[\text{ }\!\!\upsilon\!\!\text{ =}\frac{\text{2}{{\text{r}}^{\text{2}}}\left( \text{ }\!\!\rho\!\!\text{ - }\!\!\sigma\!\!\text{ } \right)\text{g}}{\text{9 }\!\!\eta\!\!\text{ }}\]pressure \[=hpg\]) (b) We know that the density of air is maximum near the surface of earth and decreases rapidly with height and at a height of about 6 km, it decreases to nearly half its value at the sea level. Beyond 6 km height the density of air decreases very slowly with height. Due to this reason, the atmospheric pressure at a height of about 6 km decreases to nearly half at value at sea level. (c) Since due to applied force on liquid, the pressure is transmitted equally in all directions inside the liquid. That is why there is no fixed direction for the pressure due to liquid. Hence hydrostatic pressure is a scalar quantity.